There is about a trillion human cells that make each one of us who we are and able to do all the things that we do, but you have 10 trillion bacterial cells in you or on you at any moment in your life. So, 10 times more bacterial cells than human cells on a human being. And of course it’s the DNA that counts, so here’s all the A, T, Gs and Cs that make up your genetic code, and give you all your charming characteristics. You have about 30,000 genes. Well it turns out you have 100 times more bacterial genes playing a role in you or on you all of your life. At the best, you’re 10 percent human, but more likely about one percent human, depending on which of these metrics you like. I know you think of yourself as human beings, but I think of you as 90 or 99 percent bacterial.

I hope when you learn things, like about how the natural world works — I just want to say that whenever you read something in the newspaper or you get to hear some talk about something ridiculous in the natural world it was done by a child. Science is done by that demographic. All of those people are between 20 and 30 years old, and they are the engine that drives scientific discovery in this country. It’s a really lucky demographic to work with. I keep getting older and older and they’re always the same age, and it’s just a crazy delightful job.